What is warfarin?
Warfarin is a prescription medicine that helps stop
the blood from clotting (coagulating). It’s called an
anti-coagulant. The brand of warfarin called
Marevan® is usually used. There is another brand
of warfarin called Coumadin®, which cannot be used
at the same time as Marevan.
Talk to your pharmacist if anything
looks different.
Why you need warfarin?
You need warfarin because you have (or may get) a
clot. Clots can be harmful if they block the blood
flow in an artery or vein.
A deep vein clot (often the leg) is called a Deep Vein
Thrombosis or DVT, in the lung it is called a
Pulmonary Embolism or PE.
If your heart beats irregularly (called Atrial
Fibrillation or AF), the blood flow can be slowed and
a clot can develop and cause a stroke. Blood clots
in the heart can cause a heart attack.
What makes clots more likely to happen?
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Being overweight
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Some inherited conditions
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Sitting or lying in one position for a long time
(for example, long flights or car journeys)
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Surgery
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Major injuries or paralysis
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Cancer and its treatments
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Pregnancy
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Hormone Replacement Therapy (HRT)
Oral contraceptives (The Pill)
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Regular Blood tests
You will need to have blood tests. The blood test
measures the speed of blood clotting and is called the INR
(International Normalised Ratio). The INR should be
anywhere between 2 and 4.
Your doctor will tell you what INR you should be
aiming for, what warfarin dose you need, and how
often you need an INR blood test.
If you are in hospital, your blood will be tested there.
When you are at home your doctor will give you a form
when necessary, to take to a laboratory.
On the day you get your blood tested:
1. Have your blood test in the morning
2. Ring in the afternoon for the result. The nurse or
doctor will tell you what dose to take in the evening.
Take the dose in the evening, and record that you have
taken the dose.
When should I take my tablets?
Take your tablets (as one dose), once a day, at the same
time every day. Evening is best, so that you can have your
blood test in the morning.
Mark the calendar when you have taken your dose, or
use a medicine organiser.
Warfarin can be taken with or without food.
What should I do if I forget a dose?
Take the missed dose as soon as you remember if it
is on the same day. However if you do not
remember until the following day, only take the dose
you would take on that day, as you should never
take more than one dose a day.
Tell your doctor about missed doses.
How long do I need to take warfarin for?
It depends on your condition. Your doctor will tell
you how long you need to take warfarin.
Other medicines, ‘over the counter’ and alternative treatments
A lot of treatments can change how warfarin works.
(for example, many antibiotics and treatments for
arthritis can increase the risk of bleeding). Even St
John’s wort, gingko, ginseng, dong quai, cranberry
juice and ginger can alter response to warfarin.
Tell your doctor and pharmacist about all the
medicines and alternative treatments you
take.
Call a doctor immediately if you have:
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Unusual bruising or bleeding
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Fever, infection
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Vomiting, diarrhoea
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Unexplained pain
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Loss of appetite for 2-3 days
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Blood in urine or faeces (black bowel
♦
motions)
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Changes to your skin (for example, a rash or
itching)